Publikační činnost Katedry aplikované mechaniky / Publications of Department of Applied Mechanics (330)

Permanent URI for this collectionhttp://hdl.handle.net/10084/106718

Kolekce obsahuje bibliografické záznamy publikační činnosti (článků) akademických pracovníků Katedry aplikované mechaniky (330) v časopisech registrovaných ve Web of Science od roku 2003 po současnost.
Do kolekce jsou zařazeny:
a) publikace, u nichž je v originálních dokumentech jako působiště autora (adresa) uvedena Vysoká škola báňská-Technická univerzita Ostrava (VŠB-TUO),
b) publikace, u nichž v originálních dokumentech není v adrese VŠB-TUO uvedena, ale autoři prokazatelně v době jejich zpracování a uveřejnění působili na VŠB-TUO.

Bibliografické záznamy byly původně vytvořeny v kolekci Publikační činnost akademických pracovníků VŠB-TUO, která sleduje publikování akademických pracovníků od roku 1990.

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Now showing 1 - 20 out of 126 results

Transverse cracking signal characterization in CFRP laminates using modal acoustic emission and digital image correlation techniques
(Elsevier, 2024) Šofer, Michal; Cienciala, Jakub; Šofer, Pavel; Paška, Zbyněk; Fojtík, František; Fusek, Martin; Czernek, Pavel
The process of formation and subsequent propagation of transverse cracks in 90 degrees plies of carbon-fiber laminated composites was studied using modal acoustic emission approach and digital image correlation techniques. The results from modal acoustic emission approach, which included a newly developed processing tool for acoustic emission waveforms, provided information for identification and subsequent characterization or localization of signals originating from transverse cracking by analysis of the separated flexural and extensional Lamb wave modes in terms of their modal parameters. The digital image correlation method served as a verification tool of the acoustic emission data outputs in the terms of activity of significant localized events originating from the formation of the transverse crack in the 90oply. This made it possible to specify more locally the accompanying activity belonging to the formation or propagation of the magistral transverse crack. The manuscript also presents results related to the evolution of flexural/extensional wave modal parameters as the function of loading force for both [0/0/0/90]S and [90/0/0/0]S panels. It can be concluded that the detection of transverse cracks requires the need for applying a more complex acoustic emission data analysis methodology, while the standard parametric analysis, including the waveform peak frequency, is not sufficient. The presented methodology may serve as a basis for development of robust analysis tool capable of detecting the investigated phenomena.
Notched structural steel specimens assessed by selected fatigue analysis methods
(Elsevier, 2024) Nesládek, Martin; Fojtík, František; Mžourek, Matěj; Papuga, Jan
This paper focuses on fatigue estimation of notched components. It discusses two major concepts – critical distance theory and solutions based on the relative stress gradient – and specific criteria related to them. It checks their quality by validating their output on own experimental data retrieved in fully-reversed tension and in fully-reversed torsion on unnotched and notched specimens manufactured from ČSN 411523 structural steel (equivalent to S355J2). The solutions based on the stress gradient provide better estimates. However, these two calculation concepts process the input data differently and use them for calibrating their parameters. Together with the limited scope of the experimental set, this has prevented the authors reaching a final verdict on ranking the estimation quality of the compared criteria. The output of our investigation shows that the solutions proposed within the concept of a relative stress gradient are currently more practical for use in the general engineering domain.
Application of Instrumented Indentation Test and Neural Networks to determine the constitutive model of in-situ austenitic stainless steel components
(Springer Nature, 2024) Ma, Quoc-Phu; Basterrech, Sebastian; Halama, Radim; Omacht, Daniel; Měsíček, Jakub; Hajnyš, Jiří; Platoš, Jan; Petrů, Jana
Over the last few decades, Instrumented Indentation Test (IIT) has evolved into a versatile and convenient method for assessing the mechanical properties of metals. Unlike conventional hardness tests, IIT allows for incremental control of the indenter based on depth or force, enabling the measurement of not only hardness but also tensile properties, fracture toughness, and welding residual stress. Two crucial measures in IIT are the reaction force (F) exerted by the tested material on the indenter and the depth of the indenter (D). Evaluation of the mentioned properties from F-D curves typically involves complex analytical formulas that restricts the application of IIT to a limited group of materials. Moreover, for soft materials, such as austenitic stainless steel SS304L, with excessive pile-up/sink-in behaviors, conducting IIT becomes challenging due to improper evaluation of the imprint depth. In this work, we propose a systematic procedure for replacing complex analytical evaluations of IIT and expensive physical measurements. The proposed approach is based on the well-known potential of Neural Networks (NN) for data-driven modeling. We carried out physical IIT and tensile tests on samples prepared from SS304L. In addition, we generated multiple configurations of material properties and simulated the corresponding number of IITs using Finite Element Method (FEM). The information provided by the physical tests and simulated data from FEM are integrated into an NN, to produce a parametric mapping that can predict the parameters of a constitutive model based on any given F-D curve. Our physical and numerical experiments successfully demonstrate the potential of the proposed approach.
Comparison of tensile and creep properties of SAC305 and SACX0807 at room temperature with DIC application
(MDPI, 2024) Paška, Zbyněk; Halama, Radim; Dymáček, Petr; Govindaraj, Bhuvanesh; Rojíček, Jaroslav
The contribution presents the verification of the methodology of accelerated creep tests from the point of view of obtaining more information about the stress-strain behaviour of the investigated materials using the Digital Image Correlation method. Creep tests are performed on SAC305 and SACX0807 lead-free solders and are supplemented by numerical modelling using the finite element method, considering the viscoplastic model based on the theory of Perzyna, Chaboche, and Norton. The stress-strain behaviour of both solders appears to be very similar at applied strain rates of 0.0002-0.0026%/s and applied creep stresses of 15-28 MPa. Initially, the viscoplastic model is calibrated using an analytical approach. Then, the finite element model updating approach is used to optimise the material parameters based on the simultaneous simulations of creep and tensile tests. As a result, the total objective function value is reduced almost five times due to optimisation. The proposed type of accelerated test with an hourglass specimen proves to be suitable for calibrating the considered class of viscoplastic models. The main benefit is that a single specimen is required to obtain creep curves on various stress levels.
Influence of meta-atom geometry on the occurrence of local resonance regions in two-dimensional finite phononic structures
(Polska Akademia Nauk, Instytut fizyki, 2023) Garus, Sebastian; Sochacki, Wojciech; Garus, Justyna; Šofer, Michal; Šofer, Pavel; Gruszka, K. M.
In this work, the influence of different cross-sections of meta-atoms and their distribution on the occurrence of local resonance regions in inter-meta-atomic spaces of finite phononic structures was investigated. Software based on the Mathematica package was designed and implemented using the finite difference algorithm in the time domain to simulate mechanical wave propagation in phononic structures. Then, for the recorded time series from the inter-meta-atomic spaces, resonant frequency distributions were determined using Fourier transforms, and an analysis of the differences in frequency distributions depending on the location of the inter-meta-atomic space was carried out.
Two contributions to rolling contact fatigue testing considering different diameters of rail and wheel discs
(MDPI, 2023) Šmach, Jiří; Halama, Radim; Marek, Martin; Šofer, Michal; Kovář, Libor; Matušek, Petr
Scaled rolling contact fatigue tests, used to practically simulate the wear of the wheel and rail material under laboratory conditions, are typically classified into two categories. Tests in the first category use twin-disc stands, while the second group of test rigs use two discs of different diameters considering the rail disc as the larger one. The latter setup is closer to the real situation, but problems can occur with high contact pressures and tractions. The focus of this paper is on two main contributions. Firstly, a case study based on finite element analysis is presented, allowing the optimization of the specimen geometry for high contact pressures. Accumulated plastic deformation caused by cycling is responsible for abrupt lateral deformation, which requires the use of an appropriate cyclic plasticity model in the finite element analysis. In the second part of the study, two laser profilers are used to measure the dimensions of the specimen in real time during the rolling contact fatigue test. The proposed technique allows the changes in the specimen dimensions to be characterized during the test itself, and therefore does not require the test to be interrupted. By using real-time values of the specimen’s dimensional contours, it is possible to calculate an instantaneous value of the slip ratio or the contact path width.
MATLAB-based algorithm and software for analysis of wavy collagen fibers
(Oxford University Press, 2023) Polzer, Stanislav; Thompson, Sarah; Vittalbabu, Swathi; Ulu, Arzu; Carter, David; Nordgren, Tara; Eskandari, Mona
Knowledge of soft tissue fiber structure is necessary for accurate characterization and modeling of their mechanical response. Fiber configuration and structure informs both our understanding of healthy tissue physiology and of pathological processes resulting from diseased states. This study develops an automatic algorithm to simultaneously estimate fiber global orientation, abundance, and waviness in an investigated image. To our best knowledge, this is the first validated algorithm which can reliably separate fiber waviness from its global orientation for considerably wavy fibers. This is much needed feature for biological tissue characterization. The algorithm is based on incremental movement of local regions of interest (ROI) and analyzes two-dimensional images. Pixels belonging to the fiber are identified in the ROI, and ROI movement is determined according to local orientation of fiber within the ROI. The algorithm is validated with artificial images and ten images of porcine trachea containing wavy fibers. In each image, 80-120 fibers were tracked manually to serve as verification. The coefficient of determination R2 between curve lengths and histograms documenting the fiber waviness and global orientation were used as metrics for analysis. Verification-confirmed results were independent of image rotation and degree of fiber waviness, with curve length accuracy demonstrated to be below 1% of fiber curved length. Validation-confirmed median and interquartile range of R2, respectively, were 0.90 and 0.05 for curved length, 0.92 and 0.07 for waviness, and 0.96 and 0.04 for global orientation histograms. Software constructed from the proposed algorithm was able to track one fiber in about 1.1 s using a typical office computer. The proposed algorithm can reliably and accurately estimate fiber waviness, curve length, and global orientation simultaneously, moving beyond the limitations of prior methods.
Design and non-linear modeling of new wind girder used for bolted tanks
(MDPI, 2023) Drahorád, Lukáš; Maršálek, Pavel; Hronček, Juraj; Rybanský, David; Šotola, Martin; Poruba, Zdeněk; Láryš, Michal
Large-capacity bolted cylindrical tanks for liquid storage are used in many applications. The tanks are made of thin steel sheets that are connected by bolts. A common problem associated with tanks is deforming under extreme loads. Adding wind girders to the tank increases the tank’s buckling capacity, which is defined as the limit load at which the structure loses stability. The girders are usually placed in the horizontal joints of the tank wall. The girders are bent from standard or non-standard steel bars with a uniform cross-section. This type of design is difficult to produce, especially with large profiles or large curvatures, to avoid distortion of the cross-section during bending. Furthermore, the girders are customized to the given openings and curvature for various tank diameters. The resulting solution is then uneconomical and more complicated to store. This paper deals with the design and non-linear modeling of a new shape of wind girder for bolted tanks that eliminates the above-mentioned disadvantages. To analyze the new shape of the girder, a non-linear numerical model of an open-topped tank with various dimensions is designed to study its buckling capacity.
Application of improved b-value and clustering analysis for structural integrity assessment of CFRP specimen under tensile loading
(Polska Akademia Nauk, Instytut Metalurgii i Inżynierii Materiałowej, 2023) Šofer, Michal; Kwiatoń, Paweł; Pavlíček, Pavel
In the present study, the evolution of different failure mechanisms in carbon fiber reinforced polymer composites is being investigated using acoustic emission technique, unsupervised clustering technique and improved b-value analysis. The experimental part involved the realization of tensile tests of different materials, namely samples with [0/90]2S uniaxial layer configuration and [0/90]2S twill fabric samples. Both types of tests were monitored using one wideband acoustic emission sensor, while the tensile tests of twill fabric samples were additionally supplemented with resonant acoustic emission sensor to perform a comparative analy sis between datasets from resonant/wideband acoustic emission sensor. The comparative study itself was preceded by the failure mechanisms characterization process, which has been performed on the tensile test dataset of [0/90]2S layer configuration with the contribution of clustering technique. The subsequent analysis of the twill fabric resonant/wideband acoustic emission sensor datasets included the improved b-value technique, which relates the magnitude of fracture with the slope of the amplitude distribution. The presented results, especially in terms of the improved b-value technique applied to individual clusters, show enhanced ability to assess in more detail the actual structural integrity depending on the applied load.
Influence of material distribution and damping on the dynamic stability of Bernoulli-Euler beams
(Polska akademia nauk, 2023) Garus, Sebastian; Garus, Justyna; Sochacki, Wojciech; Nabiałek, Marcin; Petrů, Jana; Borek, Wojciech; Šofer, Michal; Kwiatoń, Paweł
The study analyzed the influence of materials and different types of damping on the dynamic stability of the Bernoulli-Euler beam. Using the mode summation method and applying an orthogonal condition of eigenfunctions and describing the analyzed system with the Mathieu equation, the problem of dynamic stability was solved. By examining the influence of internal and external damping and damping in the beam supports, their influence on the regions of stability and instability of the solution to the Mathieu equation was determined.
Quantification and analysis of residual stresses in braking pedal produced via laser-powder bed fusion additive manufacturing technology
(MDPI, 2023) Fojtík, František; Potrok, Roman; Hajnyš, Jiří; Ma, Quoc-Phu; Kudrna, Lukáš; Měsíček, Jakub
This study focuses on the experimental verification of residual stress (RS) in a 3D-printed braking pedal using the Powder Bed Fusion (PBF) method with SS316L material. The RS was measured at two representative locations using the hole drilling method (HDM) and the dividing method, which are semi-destructive and destructive methods of RS measurement, respectively. The finite element method (FEM) was used with Ansys Workbench 2020R2 and Simufact Additive 2021 software to determine the magnitude of RS. The results provide insights into how RS is incorporated into metal 3D-printed components and the available tools for predicting RS. This information is essential for experts to improve the accuracy and functionality of SLM parts when post-subtractive or additive manufacturing processes are used. Overall, this study contributes to the advancement of knowledge on the effects of RS on 3D-printed metal components, which can inform future research and development in this area.
The disturbance influence on vibration of a belt device driven by a crank mechanism
(Elsevier, 2023) Lampart, Marek; Zapoměl, Jaroslav
As well as technological forces, real-life belt and conveyor systems are loaded by disturbing effects that have a mostly random character. To analyze importance of their influence on belt and conveyor system behavior, a computational model was set up in which the disturbances were represented by the discretization and round-off errors occurring during the solving of the governing equations, which is a new and original idea. The simulations that were carried out show that the disturbances can spawn hidden and co-existing attractors and transitions between vibrations of different periods or between regular and chaotic motions and reverse bifurcations. The main contribution of the paper is a new and original way to modeling of the systems’ inaccuracies and disturbances having frequently a random character by means of numerical inaccuracies caused by round-off errors and set tolerances of the solution methods for solving the equations of motion. The computational simulations give evidence that these factors have the same effect as inaccuracies and uncertainties of real machines on their behavior. The simulation showed that these factors can lead to qualitatively different system behavior, like the transitions between the regular and chaotic regimes. The physical validity of all operating regimes was proved by the theorem of the time change of the kinetic energy. The main goal of the presented article is to point out that small deviations from the rated state can cause qualitatively different behavior of the machine systems.
Experimental and stochastic application of an elastic foundation in loose material transport via a sandwich belt conveyor - Part 2
(MDPI, 2023) Čepica, Daniel; Frydrýšek, Karel; Hrabovský, Leopold; Nikodým, Marek
This article serves as a continuation of our previously published work and focuses on loose material transport via sandwich belt conveyors. Experimental, analytical, stochastic, and numerical approaches are used to obtain and utilize the moduli of a bilateral Winkler elastic foundation that represent a loose material, which is wheat (Triticum aestivum) that is free of bran in this case. The solutions were obtained for a uniformly and nonuniformly distributed loose material. The task of the conveyor with loose material is simplified into a symmetric task, i.e., a beam on an elastic bilateral Winkler foundation, for an analytical solution and stochastic solution (Anthill and Matlab sw). In a numerical approach, this is considered a plane strain problem within the finite element method (Ansys and MSC.Marc sw). The experimental data are evaluated and used to obtain the functions of Winkler elastic foundation moduli, which are further considered in the numerical solution. The finite element method mainly serves as a verification tool. The acquired histograms of the elastic foundation moduli can be further applied in various scientific and research fields.
Effect of aortic bifurcation geometry on pressure and peak wall stress in abdominal aorta: Fluid-structure interaction study
(Elsevier, 2023) Jagoš, Jiří; Schwarz, David; Polzer, Stanislav; Burša, Jiří
Background and Objective Geometry of aorto-iliac bifurcation may affect pressure and wall stress in aorta and thus potentially serve as a predictor of abdominal aortic aneurysm (AAA), similarly to hypertension. Methods Effect of aorto-iliac bifurcation geometry was investigated via parametric analysis based on two-way weakly coupled fluid-structure interaction simulations. The arterial wall was modelled as isotropic hyperelastic monolayer, and non-Newtonian behaviour was introduced for the fluid. Realistic boundary conditions of the pulsatile blood flow were used on the basis of experiments in literature and their time shift was tailored to the pulse wave velocity in the model to obtain physiological wave shapes. Eighteen idealized and one patient-specific geometries of human aortic tree with common iliac and renal arteries were considered with different angles between abdominal aorta (AA) and both iliac arteries and different area ratios (AR) of iliac and aortic luminal cross sections. Results Peak wall stress (PWS) and systolic blood pressure (SBP) were insensitive to the aorto-iliac angles but sensitive to the AR: when AR decreased by 50%, the PWS and SBP increased by up to 18.4% and 18.8%, respectively. Conclusions Lower AR (as a result of the iliac stenosis or aging), rather than the aorto-iliac angles increases the BP in the AA and may be thus a risk factor for the AAA development.
Avoiding disc collisions and nonlinear vibration of unbalanced rotors by means of position control of the rotor journal mounted in magnetorheological hydrodynamic bearings
(Elsevier, 2023) Zapoměl, Jaroslav; Ferfecki, Petr; Kozánek, Jan
Rotors of rotating machines are often supported by hydrodynamic bearings. Imbalance, ground vibration, assembling inaccuracies, and eccentric position of the shaft journal in the bearing hole may result in collisions between the rotors and their casings if the gap between the rotating and stationary parts is narrow. This can be avoided by controlling the position of the rotor journal in the bearing hole by changing stiffness of the oil film. This method of controlling parameters of the lubricating layer is offered by application of magnetically sensitive fluids. A new design of magnetically controllable hydrodynamic bearing was developed. The magnetic flux is generated by an electric coil. It passes through the bearing housing, and the layer of lubricant and goes back to the coil core. Magnetic induction in the bearing gap is calculated by application of the Kirchhoff and Hopkinson laws. The pressure distribution in the oil layer is obtained by solving the Reynolds equation adapted to lubricants exhibiting yielding shear stress, the magnitude of which depends on magnetic induction. Results of the computational simulations showed that application of a magnetic field acting on magnetorheological lubricant in the bearing gap makes it possible to prevent impacts between the rotor and its casing in a certain velocity interval, or at least to reduce magnitude of the impact forces if collisions occur. The principal contribution of the conducted research is the proposal of a new approach based on semiactive principle to controlling position of rotors working in limited space and obtaining more information on interaction between the rotors and magnetically controllable hydrodynamic bearings during the operating conditions when collisions between the rotor and its stationary part take place.
Optimization of control parameters of magnetorheological squeeze film dampers to minimize the vibration amplitude of rotors passing the critical speed
(MDPI, 2023) Zapoměl, Jaroslav; Ferfecki, Petr; Molčan, Michal
Rotors are often coupled with a stationary part by rolling element bearings. To suppress their excessive vibration, the bearings are inserted in squeeze film dampers. The control of damping in the support elements offers the possibility to minimize the oscillation amplitude of accelerating or decelerating rotors, passing the regions of critical speeds. The controllable damping effect can be achieved if the squeeze film dampers are lubricated with magnetorheological oil. The change in the applied current feeding the electric coil changes magnetic induction in the damper gap, which changes the oil damping properties. The minimum vibration amplitude of the rotor running up or down through the resonance area is accomplished if the current increase or decrease is not sudden, but if it is distributed in some time interval. This article concentrates on determination of the optimum parameters of this manipulation. The developed procedure leads to solving an unconstrained optimization problem with the implicit objective function. The evolution method was used for its solving. In the investigated case, the proposed procedure made it possible to reduce maximum vibration amplitude by about 40% compared with the uncontrolled current decrease. The main contribution of the conducted research work is presentation of a new and original procedure for controlling the damping effect in the rotor supports. It provides a new idea to the designers and engineers regarding how to minimize amplitude of the rotor vibration when passing the critical speed. In addition, the article points to a new area of utilization of controllable magnetorheological squeeze film dampers.
Simplified numerical model for determining load-bearing capacity of steel-wire ropes
(MDPI, 2023) Hronček, Juraj; Maršálek, Pavel; Rybanský, David; Šotola, Martin; Drahorád, Lukáš; Lesňák, Michal; Fusek, Martin
Steel-wire rope is a mechanical component that has versatile uses and on which human lives depend. One of the basic parameters that serve to describe the rope is its load-bearing capacity. The static load-bearing capacity is a mechanical property characterized by the limit static force that the rope is able to endure before it breaks. This value depends mainly on the cross-section and the material of the rope. The load-bearing capacity of the entire rope is obtained in tensile experimental tests. This method is expensive and sometimes unavailable due to the load limit of testing machines. At present, another common method uses numerical modeling to simulate an experimental test and evaluates the load-bearing capacity. The finite element method is used to describe the numerical model. The general procedure for solving engineering tasks of load-bearing capacity is by using the volume (3D) elements of a finite element mesh. The computational complexity of such a non-linear task is high. Due to the usability of the method and its implementation in practice, it is necessary to simplify the model and reduce the calculation time. Therefore, this article deals with the creation of a static numerical model which can evaluate the load-bearing capacity of steel ropes in a short time without compromising accuracy. The proposed model describes wires using beam elements instead of volume elements. The output of modeling is the response of each rope to its displacement and the evaluation of plastic strains in the ropes at selected load levels. In this article, a simplified numerical model is designed and applied to two constructions of steel ropes, namely the single strand rope 1 × 37 and multi-strand rope 6 × 7-WSC.
Analysis of the influence of thermal loading on the behaviour of the Earth’s crust
(MDPI, 2023) Wandrol, Ivo; Frydrýšek, Karel; Čepica, Daniel
The article focuses on the deformation and strain-stress analysis of the Earth’s crust under external thermal loading. More specifically, the influence of cyclic changes in the surface temperature field on the stress and displacement inside the crust over a two-year time span is investigated. The finite element program MSC.Marc Mentat was used to calculate the stresses and displacements. For practical analysis reasons, the Earth’s crust is simplified as a planar, piecewise homogeneous, isotropic model (plane strain), and time-varying temperature functions of illumination (thermal radiation) from the Sun are considered in the local isotropy sections of the model. Interaction between the Earth’s crust and mantle is defined by the Winkler elastic foundation. By applying a probabilistic approach (Monte Carlo Method), a new stochastic model of displacements and stresses and new information on crustal displacements relative to the Earth’s mantle were obtained. The results proved the heating influence of the Sun on the Earth’s crust and plate tectonics.
Experimental and stochastic application of an elastic foundation in loose material transport via sandwich belt conveyors
(MDPI, 2023) Frydrýšek, Karel; Čepica, Daniel; Hrabovský, Leopold; Nikodým, Marek
This article deals with the problem of loose materials, i.e., wheat grain, when transported by belt conveyors with cover belts. For the purpose of further research, experimental measurements of the deflections of a conveyor belt with loose material were carried out on a self-built laboratory test device. The mechanical contact between the wheat and the belt could be suitably approximated using an elastic foundation. The measured data were evaluated and used to obtain functional relationships for the compressibility moduli of the bilateral Winkler elastic foundation. The obtained relationships were further stochastically processed using the Monte Carlo method.
Acoustic emission signal characterisation of failure mechanisms in CFRP composites using dual-sensor approach and spectral clustering technique
(MDPI, 2023) Šofer, Michal; Šofer, Pavel; Pagáč, Marek; Volodarskaja, Anastasia; Babiuch, Marek; Gruň, Filip
The characterisation of failure mechanisms in carbon fibre-reinforced polymer (CFRP) materials using the acoustic emission (AE) technique has been the topic of a number of publications. However, it is often challenging to obtain comprehensive and reliable information about individual failure mechanisms. This situation was the impetus for elaborating a comprehensive overview that covers all failure mechanisms within the framework of CFRP materials. Thus, we performed tensile and compact tension tests on specimens with various stacking sequences to induce specific failure modes and mechanisms. The AE activity was monitored using two different wideband AE sensors and further analysed using a hybrid AE hit detection process. The datasets received from both sensors were separately subjected to clustering analysis using the spectral clustering technique, which incorporated an unsupervised k-means clustering algorithm. The failure mechanism analysis also included a proposed filtering process based on the power distribution across the considered frequency range, with which it was possible to distinguish between the fibre pull-out and fibre breakage mechanisms. This functionality was particularly useful in cases where it was evident that the above-mentioned damage mechanisms exhibited very similar parametric characteristics. The results of the clustering analysis were compared to those of the scanning electron microscopy analysis, which confirmed the conclusions of the AE data analysis.

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